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Astron. Astrophys. 351, 47-58 (1999)

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2. Description of the objects

Our sample consists of the following objects:

  • SMM J02399-0136 ([FORMULA]2.80) is described in detail by Ivison et al. (1999). We summarize here the main properties. This source is an hyperluminous active galaxy detected in a submm survey with SCUBA. It is gravitationally lensed by a foreground cluster, which amplifies its luminosity by a factor of 2.5. Optical imaging shows two main optical components (named L1 and L2 by Ivison et al. 1998 [IV98 thereafter]) separated by [FORMULA] 3 arc sec. Both components emit weak continua and narrow emission lines ([FORMULA]1000-1500 km s-1) that show a type 2 AGN in L1 (Seyfert or narrow line quasar). Radio observations reveal a very weak extended source. The far infrared (FIR) luminosity is (after correction for lensing) [FORMULA]5 times higher than in the hyperluminous Seyfert 2 FSC10214+4724 (although uncertainties remain about the exact amplification in this object). It is not clear whether the bulk of IR emission is due to dust heated by the active nucleus or by stars. If OB stars are responsible, the FIR luminosity indicates a star forming rate (SFR) (M[FORMULA]10 [FORMULA]) of [FORMULA]2000 [FORMULA] yr-1. The source has been also detected in CO showing an unresolved ([FORMULA]5 arc sec) emission spatially coincident with L1. The gas mass implied by the data is [FORMULA]1011 [FORMULA]. IV98 propose that this source is associated with a massive starburst.

  • MRC2025-218 ([FORMULA]2.63) was observed by McCarthy et al. (1990) as part of a sample of southern hemisphere radio galaxies selected from the Molongo Reference Catalogue. HST images show that the host galaxy has a compact morphology in the optical (UV rest frame), consisting of a bright nucleus and two smaller components. Extended low surface brightness emission elongated and aligned with the radio axis is also detected. The galaxy is embedded in a very large halo of ionized gas extended well beyond the radio source (Pentericci et al. 1999, McCarthy et al. 1990). Near-IR images (optical rest frame) show that the galaxy is quite compact (McCarthy et al. 1992, van Breugel et al. 1998) and fairly symmetric.

    The UV (rest-frame) spectrum shows strong, spatially extended emission lines (McCarthy et al. 1990, Villar-Martín et al. 1999, VBF99 hereafter), that reveal complex kinematics in the extended gas. Strong continuum emission aligned with the radio axis is also detected. Its nature is uncertain but its high level of polarization (Cimatti et al. 1994) shows that the contribution of a scattered component is important. The authors found that the rest frame UV continuum emission is linearly polarized ([FORMULA]8.3[FORMULA]2.3%) with the electric vector perpendicular to the UV emission axis. Any valid model for the spectral energy distribution (SED) requires at least two components: a polarized scattered component in the UV and a redder, probably unpolarized component, best represented by an evolved stellar population with a minimum age of about 2 Gyr. A nebular component associated with the line emitting gas is also required.

  • MRC1558-003 ([FORMULA]2.53) was part of the sample of ultra steep spectrum (USS) radio sources of Röttgering et al. (1995). R band CCD images show a rather small source extended ([FORMULA]1.8 arc sec is the largest extension) along position angle (PA) 50o. The radio axis PA is 75o (Röttgering et al. 1994). UV (rest frame) spectroscopy shows strong Ly[FORMULA] emission along the radio axis direction with a bright component and more diffuse emission extending for at least 15 arc sec. CIV is also extended. The lines show complex kinematics in the extended gas with FWHM[FORMULA]1000-1500 km s-1 (VMBF99).

  • MRC2104-242 ([FORMULA]2.49) was also observed by McCarthy et al. (1990) selected from the Molongo Reference Catalogue. Broad band images (McCarthy et al. 1990) show two bright clumps between the radio lobes and aligned with them. Narrow band Ly[FORMULA] images show emission extended over more than 15 arc sec along the radio axis. A large halo of diffuse emission seems to surround the entire object. The two main blobs emit continuum and strong emission lines. UV (rest frame) spectroscopy reveals complex kinematics with FWHM[FORMULA]1500 km s-1 (McCarthy et al. 1996, VMBF99). HST images (Pentericci et al. 1999) show that the host galaxy is very clumpy. There is also a narrow filament extending for [FORMULA]2 arc sec and aligned with the radio axis within a few degrees.

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© European Southern Observatory (ESO) 1999

Online publication: November 2, 1999
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